The author tries to give a definition of  'a psychiatric bed'. The many differences between the beds, on which psychiatric patients are treated, are noticed. All those differences between psychiatric beds do not deliver a basis for a good planning. The number of categories of psychiatric beds has to be reduced to a few ones. Three categories are proposed on the basis of the distinction of all psychiatric patients in those suffering from a reversible process and those suffering from an irreversible defect; the third is the category of the exceptional groups.